1. Field of the Invention
The present invention relates to a light-emitting device such as an organic electroluminescence device (referred to as “organic EL device” hereinafter).
2. Description of the Related Art
Development of light-emitting device displays is being actively pursued. Japanese Patent Laid-Open No. 2003-234179 (JP '179) discloses an invention related to an organic EL device display (OLED display).
FIG. 1 shows an OLED display described in JP '179. The OLED display includes an optically transparent substrate 1, a first electrode 2, an organic film 6, a second electrode 9, a diamond-like carbon film (DLC film) 10, a protective film 12, a first protective film 13, a second protective film 15, and an optical compensation film 18. FIG. 1 corresponds to the third embodiment in JP '179.
According to JP '179, “DLC film” means a diamond-like carbon film.
In FIG. 1, the DLC film is the layer that lies between the layer indicated by reference numerals 15 and 18 and the layer indicated by reference numerals 13 and 17. The DLC film has substantially the same shape as that of the layer indicated by reference numerals 13 and 17. It should be noted here that reference numeral 10 and the lead line therefor are omitted from the drawing.
Paragraph [0013] of JP '179 discloses optical compensation film 18 as being transparent and having an antireflection function, a lens-collimation function, etc., and further that optical compensation film 18 is laminated on second protective film 15.
Paragraph [0011] of JP '179 describes use of a transparent acrylic resin 17 as the first protective film 13. In other words, the first protective film 13 is composed of a transparent acrylic resin.
As indicated by dashed arrows in the drawing, light is extracted toward the upper side of the OLED display.
Although the document discloses the antireflection function of optical compensation film 18, no specific description thereof is provided. Persons skilled in this art will interpret the phrase “antireflection function” to mean the function of preventing the reflection of ambient light at the optical compensation film.
However, the present inventors have made the following discovery during the development of organic EL devices with regard to reflection of ambient light.
When an organic EL device is used in a display surface, the visibility of the display surface decreases by the influence of ambient light. This is because ambient light that enters the device is reflected at an electrode remote from the observer and is emitted back to the exterior of the device.
In other words, the present inventors have found that in order to improve visibility of the display surface, it is more important to prevent ambient light that enters the device from being reflected back to the exterior of the device than to prevent reflection of ambient light at the outer surface of the device.
However, JP '179 provides no means for preventing ambient light entering the device from being reflected back to the exterior of the device. If the device disclosed in JP '179 is to completely prevent ambient light from entering the device, then optical compensation film 18 must be an optically opaque member. However, if the film is optically opaque, it is substantially impossible to extract the light emitted by the device itself.